A117368 - cp's OEIS frontend

A117368 a(n) = largest prime less than the smallest prime dividing (2n-1).

n	a(n)
2	2
3	3
4	5
5	2
6	7
7	11
8	2
9	13
10	17
11	2
12	19
13	3
14	2
15	23
16	29
17	2
18	3
19	31
20	2
21	37
22	41
23	2
24	43
25	5
26	2
27	47
28	3
29	2
30	53
31	59
32	2
33	3
34	61
35	2
36	67
37	71
38	2
39	5
40	73
41	2
42	79
43	3
44	2
45	83
46	5
47	2
48	3
49	89
50	2
51	97
52	101
53	2
54	103
55	107
56	2
57	109
58	3
59	2
60	5
61	7
62	2
63	3
64	113
65	2
66	127
67	5
68	2
69	131
70	137
71	2
72	7
73	3
74	2
75	139
76	149
77	2
78	3
79	151
80	2
81	5
82	157
83	2

[2, 3, 5, 2, 7, 11, 2, 13, 17, 2, 19, 3, 2, 23, 29, 2, 3, 31, 2, 37, 41, 2, 43, 5, 2, 47, 3, 2, 53, 59, 2, 3, 61, 2, 67, 71, 2, 5, 73, 2, 79, 3, 2, 83, 5, 2, 3, 89, 2, 97, 101, 2, 103, 107, 2, 109, 3, 2, 5, 7, 2, 3, 113, 2, 127, 5, 2, 131, 137, 2, 7, 3, 2, 139, 149, 2, 3, 151, 2, 5, 157, 2]

cp's OEIS Frontend

A117368 a(n) = largest prime less than the smallest prime dividing (2n-1).

Table of values

List of values

n	a(n)
2	2
3	3
4	5
5	2
6	7
7	11
8	2
9	13
10	17
11	2
12	19
13	3
14	2
15	23
16	29
17	2
18	3
19	31
20	2
21	37
22	41
23	2
24	43
25	5
26	2
27	47
28	3
29	2
30	53
31	59
32	2
33	3
34	61
35	2
36	67
37	71
38	2
39	5
40	73
41	2
42	79
43	3
44	2
45	83
46	5
47	2
48	3
49	89
50	2
51	97
52	101
53	2
54	103
55	107
56	2
57	109
58	3
59	2
60	5
61	7
62	2
63	3
64	113
65	2
66	127
67	5
68	2
69	131
70	137
71	2
72	7
73	3
74	2
75	139
76	149
77	2
78	3
79	151
80	2
81	5
82	157
83	2

n	a(n)
2	2
3	3
4	5
5	2
6	7
7	11
8	2
9	13
10	17
11	2
12	19
13	3
14	2
15	23
16	29
17	2
18	3
19	31
20	2
21	37
22	41
23	2
24	43
25	5
26	2
27	47
28	3
29	2
30	53
31	59
32	2
33	3
34	61
35	2
36	67
37	71
38	2
39	5
40	73
41	2
42	79
43	3
44	2
45	83
46	5
47	2
48	3
49	89
50	2
51	97
52	101
53	2
54	103
55	107
56	2
57	109
58	3
59	2
60	5
61	7
62	2
63	3
64	113
65	2
66	127
67	5
68	2
69	131
70	137
71	2
72	7
73	3
74	2
75	139
76	149
77	2
78	3
79	151
80	2
81	5
82	157
83	2

n	a(n)
2	2
3	3
4	5
5	2
6	7
7	11
8	2
9	13
10	17
11	2
12	19
13	3
14	2
15	23
16	29
17	2
18	3
19	31
20	2
21	37
22	41
23	2
24	43
25	5
26	2
27	47
28	3
29	2
30	53
31	59
32	2
33	3
34	61
35	2
36	67
37	71
38	2
39	5
40	73
41	2
42	79
43	3
44	2
45	83
46	5
47	2
48	3
49	89
50	2
51	97
52	101
53	2
54	103
55	107
56	2
57	109
58	3
59	2
60	5
61	7
62	2
63	3
64	113
65	2
66	127
67	5
68	2
69	131
70	137
71	2
72	7
73	3
74	2
75	139
76	149
77	2
78	3
79	151
80	2
81	5
82	157
83	2